1. Field of the Invention
The invention relates to a circuit arrangement for connecting an electrical consumer to an alternating voltage source, wherein the electrical consumer is connected in series with a switch actuator and the switch actuator is associated with an electronic circuit whose direct voltage supply is carried out by the switch actuator.
2. Prior Art
Circuit arrangements of this generic type are known. These are used in residential wiring, for example, where electrical consumers are intended to be variably controllable by way of a bus and the wiring is carried out in a so-called two-wire technique (phase is connected through, no neutral conductor). A typical application example is the switching on and off of a light. Triacs or thyristors are used in a known manner as switch actuators which, in the alternating voltage circuit, can be brought into a high-impedance (off) state or a low-impedance (on) state as possible switching states. These are triggered by way of an electronic circuit which receives its direct voltage supply from the triac or the thyristor. If the triac or the thyristor is in the high-impedance state, a circuit for generating constant voltage, as a direct voltage source for the electronic circuit, is supplied with power via a capacitive or inductive series resistor. Usually Zener diodes or reference diodes are used as constant voltage generators in this connection.
In order to trigger the electrical consumers, the triac or the thyristor, when in the low-impedance state, are operated in phase-angle control, i.e. with each half-wave of the alternating voltage, the thyristor or the triac is connected through when the corresponding voltage required for this triggering has built up in the constant voltage generator.
In the known circuit arrangement, it is disadvantageous that in the high-impedance state of the switch actuator, only a relatively low current is available to the electronic circuit and this current is limited by the internal resistance of the electrical consumer. The higher the internal resistance of the electrical consumer, the lower the available power. It is also disadvantageous that in the low-impedance state of the switch actuator, the phase-angle control withholds a significant portion of the available voltage and therefore power from the electrical consumer. As a result of this, the electrical consumer cannot achieve its nominal power, particularly when it has a relatively low nominal power.